This invention relates to web-laying machinery such as cross-lapping or cross-folding machinery or parallel-laying machinery such as may be used in the textile, particularly the non-wovens, industry, to make a fleece out of a card web for example.
Such machinery comprises reciprocating carriage means which receive the card web on aprons and direct the end of the web on to conveyor means in such manner as to fold it on itself to build up a multi-layer fleece. A cross-lapper or cross-folder reciprocates the carriage means transversely to the direction of travel of the receiving conveyor means so that a ribbon of fleece is built up in which the fibres of a card web are substantially transversely aligned. A parallel-laying machine reciprocates the web parallel to the direction of travel of the receiving conveyor so that the card web fibres will lie parallel to the lengthwise direction of the ribbon of fleece so formed.
Web-laying machines are essentially solidly constructed mechanical devices, electrically driven, with considerable inertia in the reciprocating carriage means. While the operation of the machinery is usually as precise as may be expected from machinery of its size and weight, the effects of even small variations can often have a substantial effect upon the properties of the fleece produced thereby. For example, when the speed of operation is changing, as on start-up, the inertia of the carriage will give rise to a variation in the traverse width, because the mechanical interconnection between the carriage and the receiving conveyor, which determines the fleece width, the number of layers and other fleece characteristics, will react differently at different speeds. Other variations might appear as the result of voltage fluctuations, or the properties of resilient or pneumatic reversal-assisting buffers, or dimensional changes in aprons with age or ambient conditions, which might have the effect of producing a fleece which is too wide or too narrow or too heavy or too thick, or irregular in any of those regards.
The present invention provides a control system for a web-laying machine which overcomes these problems.